The kinetic energy present in flowing fluids, such as wind or water, has been successfully applied towards productive human ends, such as grinding grain or pumping water. Wind-powered generators were developed to harness these fluid flows for the production of electricity. Today, wind-powered generators take on the largely ubiquitous form of a turbine, or rotating airfoil. While these turbine-based wind generators are generally useful in certain open spaces with consistently high-speed winds, drawbacks still exist, such as heavy initial capital costs, low efficiency at all but a narrow range of wind speeds, the lack of cost effectiveness at lower power outputs levels (<1 kW), etc.
To circumvent the drawbacks of the turbine-based devices, various alternative generators were designed to utilize other natural flow phenomena. However, these proposals were not satisfactory due to design complexities, added cost, the need for a complex mounting structure, low efficiency in energy production, insufficient power generation, inefficient production of vibrations, restriction to high flow speeds, etc.
This disclosure describes various embodiments of unique generators that effectively promote oscillations induced by flowing fluids, and utilize the oscillations in generating electricity or other types of energy. In one aspect, an exemplary generator harnesses the energy of fluid flows by way of a combination of flutter and vortices shedding induced along a tensioned membrane, or “belt”, fixed at two or more points. The membrane may have an elongated shape or other kinds of shape that are known to promote vibrations with the flowing fluids.
An exemplary electrical generator includes at least one magnetic field generator, at least one electrical conductor, and at least one flexible membrane having at least two fixed ends. The membrane vibrates when subject to a fluid flow. One of the electrical conductor and the magnetic field generator is attached to the membrane and configured to move with the membrane. The vibration of the membrane caused by the fluid flow causes a relative movement between the electrical conductor and the applied magnetic field. The relative movement causes a change in the strength of the magnetic field applied to the electrical conductor, and the change in the strength of the magnetic field applied to the electrical conductor induces a current flowing in the conductor. One or all parts of the generator may be implemented as a MEMS (Micro Electro-Mechanical Systems) device. In one aspect, the direction of the magnetic field may be substantially perpendicular to an area enclosed by the electrical conductor, when the membrane does not vibrate.
The exemplary generator may further include at least one mass attached to the membrane, to promote movements or vibrations of the membrane when it is subject to fluid flows. In one embodiment, a power conditioning circuit may be provided to condition the induced current. The power conditioning circuit may include a rectifying circuit configured to rectify the current. In another embodiment, the magnetic field generator includes at least one permanent magnet. In still another embodiment, an exemplary generator includes multiple sets of electrical conductors, such as coils. The currents generated by the multiple sets of conductors may be combined in a serial manner. A rechargeable electrical power storage device, such as a battery or capacitor may be provided to be charged by the current or currents.
In one embodiment, the exemplary generator further includes a supporting structure. The fixed ends of the membrane are affixed to the supporting structure. The electrical conductor is attached to the membrane. The magnetic field generator is disposed on the supporting structure. In another embodiment, the magnetic field generator is attached to the membrane, and the electrical conductor is disposed on the supporting structure. In another embodiment, the magnetic field generator is oriented so as to project the magnetic field (i.e., pole to pole axis) perpendicular to the plane of the membrane. In still another embodiment, the magnetic field generator is oriented so as to project the magnetic field parallel to the plane of the membrane. Of course, the electrical conductors are rearranged in each corresponding embodiment to account for changes in the magnetic field direction.
According to another embodiment, the exemplary generator includes an adjustable tension provider, such as a motor, configured to apply an adjustable tension force between the fixed ends of the membrane according to the speed of the fluid flow. A sensor may be provided to generate a signal indicating an effect of the fluid flow. In one aspect, the tension force is adjusted based on the current.
According to another embodiment, the exemplary generator may include multiple flexible membranes. In one aspect, the membranes may affix to the same supporting structure.
Additional aspects and advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only exemplary embodiments of the present disclosure are shown and described, simply by way of illustration of the best mode contemplated for carrying out the present disclosure. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.